The invention relates to a torque converter coupling to a crankshaft in the transmission line of a motor vehicle and a method of coupling a torque converter to a crankshaft.
It is known to provide, in the transmission line of a motor vehicle, a driving coupling for the torque transmission by means of a shaft-hub coupling provided with longitudinal toothings, for a releasable coupling of a crankshaft with a hydrodynamic torque converter arranged in a coaxial manner. The longitudinal toothings of the shaft-hub coupling have tooth cross-sections which become larger and smaller respectively in the longitudinal direction of the teeth.
German Patent Document DE 197 47 962 A1 describes such a driving coupling for torque transmission. It was found that, because of the requirement of the self-locking of the driving coupling against releasing forces during torque transmission, the tooth flanks of the tooth cross-sections which become larger and smaller respectively must be made in a very precise manner, resulting in high manufacturing costs. In addition, as a result of misalignments between the torque converter and the crankshaft result in a poor contact pattern of the tooth flanks, which is always disadvantageous during torque transmission.
It is therefore an object of the invention to provide a releasable coupling between a torque converter and a crankshaft which can be established easily and compensates misalignments with zero backlash.
According to the invention, a driving coupling is provided in the transmission line of a motor vehicle for torque transmission by means of a shaft-hub coupling. The shaft-hub coupling has longitudinal toothings for a releasable coupling of a crankshaft with a hydrodynamic torque converter arranged in a coaxial manner. The longitudinal toothings of the shaft-hub coupling have tooth cross-sections which become larger and smaller respectively in the longitudinal direction of the teeth. The driving coupling has an elastomer layer situated at least between the tooth flanks of the shaft and the hub.
Such a longitudinal toothing with an elastomer layer between the shaft and the hub has the advantage that zero backlash is created in the case of an axial prestressing even when misalignments occur between the crankshaft and the torque converter. In addition, in the case of a coupling between a crankshaft and a hydrodynamic torque converter arranged coaxially, a good contact pattern is achieved by means of such a shaft-hub coupling, even in the case of an external centering.
In a preferred embodiment of the invention, the elastomer layer is applied to the shaft toothing and/or to the hub toothing. This has the advantage that the shaft-hub coupling can be produced in a simple manner, particularly if the elastomer layer is vulcanized onto the toothing.
An advantageously cost-effective variant of the driving coupling is characterized in that the longitudinal toothings of the shaft-hub coupling are shaped of sheet metal.
If the tooth cross-sections, which become larger and smaller respectively in the longitudinal direction of the teeth, are achieved by way of such a change of the tooth width of the longitudinal toothings of the shaft-hub coupling, a relatively large change of the tooth cross-section is possible as a result of the high coefficient of friction between the elastomer and the steel. This results in zero backlash even in the case of small axial tolerances. Preferably, a wedge angle of the widening or narrowing teeth from 8 to 15 degrees may be provided.
In another advantageous embodiment of the invention, an axial force is used for the axial fixing of the shaft-hub coupling, which axial force is generated by an internal converter pressure during the operation of the converter.
Such a construction has the advantage that no additional measures have to be taken for axially securing the shaft-hub coupling. The axial force in the direction of the crankshaft generated on the basis of the torque converter operation presses the conical longitudinal toothings into one another without backlash as a result of the elastomer layer.
In addition, for the axial fixing of the shaft-hub coupling, the shaft and the hub can also be form-lockingly connected with one another in a form locking manner. This ensures the coupling between the crankshaft and the torque converter even when the torque converter is not in operation and therefore no internal converter pressure is present. Such a form-locking coupling of the shaft and the hub is achieved by known machine elements, such as a tension spring mounted in a circumferential groove of the hub, or screws screwed in the radial direction into the hub and projecting through the latter.